Airtech Studios BEU for ARP 9, ARP 556, Raider L 2.0ERelieve a cramped environment for your MOSFET and cables to sit to prevent it from over bending and damage.Utilize larger battery capacity - perfect if you're running the G&G; drum mag as a support role.Eliminates the unsteady butt-stock by locking down the two metal rails!Maximum battery size approx152mm long x 19.5mm wide x 11.75mmOnce installed, the ARP9/556 remains just as compact as before - perfect for CQB use!Compatible also with the G&G; CM16 Raider L 2.0 E